Tropical Storm Humberto could merge with another developing storm, causing a weather event known as the Fujiwhara effect.
The National Hurricane Center said late Thursday morning, Tropical Storm Humberto is “gaining strength” and is expected to become a hurricane in the central Atlantic in the next day or so. CNN Weather reports Humberto will most likely stay west of Bermuda by early next week.
Forecasters are also on the lookout for thunderstorms currently moving through the northern Caribbean, which are highly probable to develop into Tropical Storm Imelda, according to CNN meteorologists. The new tropical storm will develop near the Bahamas over the weekend, meteorologists predict.
CNN Weather laid out three scenarios with these two storms: If Imelda is weaker than Humberto, Humberto could pull Imelda out to sea. But if Imelda is stronger, it could “resist Humberto’s pull and take a path that threatens the Southeast.”

The third scenario is called the Fujiwhara effect, which is when two storms pass close enough to each other that they begin an “intense dance around their common center,” as the National Weather Service puts it.
CBS News meteorologist Nikki Nolan said, “With the two tropical troubles currently north of the Caribbean, these two may interact under the Fujiwhara effect in the days ahead.”
But because the developing storm “appears to be much weaker than Humberto and several miles away from it,” if the two do interact, it may not result in a “dance.”

The National Weather Service explains that if one hurricane is stronger than the other, the smaller one will “orbit it and eventually come crashing into its vortex to be absorbed.”
If the storms are closer in strength, they could merge or spin around each other before going on their own paths.
It’s rare that the two storms would come together as one larger storm, the service notes.